1. Field of the Invention
The present invention relates to an electrical connector, more particularly to an electrical connector compatible to standard Universal Serial Bus (USB) 2.0 connector.
2. Description of Related Art
Recently, personal computers (PC) are used of a variety of techniques for providing input and output. Universal Serial Bus (USB) is a serial bus standard to the PC architecture with a focus on computer telephony interface, consumer and productivity applications. The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standard body incorporating leading companies from the computer and electronic industries. USB can connect peripherals such as mouse devices, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, external storage, networking components, etc. For many devices such as scanners and digital cameras, USB has become the standard connection method.
As of 2006, the USB specification was at version 2.0 (with revisions). The USB 2.0 specification was released in April 2000 and was standardized by the USB-IF at the end of 2001. Previous notable releases of the specification were 0.9, 1.0, and 1.1. Equipment conforming to any version of the standard will also work with devices designed to any previous specification (known as: backward compatibility).
USB supports three data rates: 1) A Low Speed rate of up to 1.5 Mbit/s (187.5 KB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks; 2) A Full Speed rate of up to 12 Mbit/s (1.5 MB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed; 3) A Hi-Speed rate of up to 480 Mbit/s (60 MB/s). Though Hi-Speed devices are commonly referred to as “USB 2.0” and advertised as “up to 480 Mbit/s”, not all USB 2.0 devices are Hi-Speed. Hi-Speed devices typically only operate at half of the full theoretical (60 MB/s) data throughput rate. Most Hi-Speed USB devices typically operate at much slower speeds, often about 3 MB/s overall, sometimes up to 10-20 MB/s. A data transmission rate at 20 MB/s is sufficient for some but not all applications. However, under a circumstance transmitting an audio or video file, which is always up to hundreds MB, even to 1 or 2 GB, currently transmission rate of USB is not sufficient. As a consequence, faster serial-bus interfaces are being introduced to address different requirements. PCI Express, at 2.5 GB/s, and SATA, at 1.5 GB/s and 3.0 GB/s, are two examples of High-Speed serial bus interfaces.
From an electrical standpoint, the higher data transfer rates of the non-USB protocols discussed above are highly desirable for certain applications. However, these non-USB protocols are not used as broadly as USB protocols. Many portable devices are equipped with USB connectors other than these non-USB connectors. One important reason is that these non-USB connectors contain a greater number of signal pins than an existing USB connector and are physically larger as well. For example, while the PCI Express is useful for its higher possible data rates, a 26-pin connectors and wider card-like form factor limit the use of Express Cards. For another example, SATA uses two connectors, one 7-pin connector for signals and another 15-pin connector for power. Due to its clumsiness, SATA is more useful for internal storage expansion than for external peripherals.
The existing USB connectors have a small size but low transmission rate, while other non-USB connectors (PCI Express, SATA, et al) have a high transmission rate but large size. Neither of them is desirable to implement modern high-speed, miniaturized electronic devices and peripherals. To provide a kind of connector with a small size and a high transmission rate for portability and high data transmitting efficiency is much desirable. In 2007, led by Intel, a technology named USB 3.0 is developed by Intel, HP, NEC, NXP semiconductor, and TI etc which realize rapid, instant signal transmission.
USB 3.0 is compatible with USB 2.0 very well and adds another set of contacts for high-speed signal transmission based on USB 2.0. The added set of contacts comprises two pairs of differential contacts and a grounding contact located between the two pairs of differential contacts for suppressing cross-talk when high-speed signal transmission. The problem existed at present is how to assemble two sets of contacts to the same insulative housing or how to manufacture an insulative housing capable of containing two sets of contacts because of compact size of current USB 2.0. Usually, for saving space, many manufacturers utilize insert-molding technology to mold one set of contacts together with an insulative housing, and then assemble the other set of contacts to the insulative housing. However, insert-molding technology is relatively expensive, and with relatively high doorsill, it is not beneficial for manufacturers to decrease prices of the electrical connector and improve competition ability thereof. Further, because electrical connectors are mounted on a printed circuit board which is equipped with a lot of electric components. When a pair of connectors mates with each other, the ESD (electrostatic discharge) phenomenon generates as the pair of connectors carry contrary charges. Actually, when people contact the electrical connectors or the contacts of the connectors, ESD can be generated. When the environmental humidity is below 50%, the instant voltage generated by static charge of people exceeds above 20000 voltages. In general, the current generated by ESD is small, but the voltages generated by ESD is capable of destroying some electric components thoroughly, especially electronic components mounted on the printed circuit board. Hence, when the connectors are mounted on the printed circuit board, they are prone to being destroyed if there is an ESD phenomenon.
Hence, it is desired to design an improved electrical connector to address the problems mentioned above.